Yes - I agree - insurance. I would also use a plug of foam to fill extra space.

Ignition in straight sided cases, is the most difficult of all, due i suspect, the easy with which smokeless powder can be pushed away from the primer flash, but the pressure front of the flash.

John Buhmiller (Old John) of Kalispel Montana went to great lengths and experimentation to achieve good ignition from straight cases.

In my own .458 American, I tested one of his ideas, of having a primer, cup-down, on top of the powder, the bullet's base holding it in place (full load, not reduced). I found that with a magnum or standard primer over the powder, cup-down, I could achieve the same ballistics using 6gr. less powder, so a drop tube was not needed, whereas to get that extra 6gr. powder & bullet into the case, I needed the 28" tube.

You are on your own, as I was however I did have very good results. This clearly shows poor ignition and powder burning with standard magnum primers. I had been using CCI250's and Federal 215's at that time - this was in the 1980's.